Interfacial tension and emulsification controllable oil displacement system and its application in conglomerate reservoirs

Abstract

The present invention relates to the fields of oilfield chemistry and oil and gas production technology, specifically to an oil displacement system with controllable interfacial tension and emulsification, and its application in conglomerate reservoirs. The oil displacement system comprises the following components, by weight: a water-soluble surfactant: 0.2%-0.3%; an oil-soluble surfactant: 0.001%-0.003%; a thickener: 0.12%-0.15%; an emulsification modifier: 1%-2%; the balance being water. This system offers the advantages of controllable interfacial tension and emulsification, and low interfacial tension throughout the entire process.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry and oil and gas production, and in particular to an oil displacement system with controllable interfacial tension and emulsification and its application in conglomerate reservoirs. Background Art

[0002] Chemical flooding, represented by binary composite flooding, is the main successor technology for improving oil field recovery. However, it is difficult to achieve ultra-low interfacial tension by using only petroleum sulfonates in binary flooding formulas. It is also difficult to maintain ultra-low interfacial tension throughout the migration in the formation. It is necessary to find other types of surfactants for compounding to improve interfacial tension and reduce the adsorption amount of surfactants.

[0003] Gemini surfactants are two or more identical or nearly identical surfactant monomers chemically linked by a linker group at or near the hydrophilic head group. Gemini surfactants are increasingly used in combined flooding formulations due to their excellent interfacial tension-reducing properties.

[0004] For example, the prior art (Wang Xueyuan. Synthesis and Characterization of Sulfonate-Type Gemini Surfactants: [Master's Thesis], Tianjin University, Tianjin: 2004) discloses the development of anionic gemini alkylbenzene sulfonates, but does not yet address how to control the degree of emulsification. The prior art (Yang Jianjun. Basic Research on the Application of Cationic Gemini Surfactants in Tertiary Oil Recovery, [PhD Thesis]: Southwest Petroleum University, Chengdu: 2005) discloses the research on cationic gemini oil displacement agents, which can reduce the interfacial tension to 10 in the absence of alkali and at low concentrations. -3 However, whether the interfacial tension of this type of cationic gemini surfactant can be maintained at an ultra-low level throughout the entire process has not been experimentally confirmed, nor has its emulsification properties been tested, and there have been no subsequent studies reporting whether it can be combined with anionic sulfonates.

[0005] Oil-water emulsification is a common phenomenon in the study of interfacial chemistry. In tertiary oil recovery (TER), emulsification of the displacement fluid with formation crude oil is one of the primary mechanisms for enhanced oil recovery through combined flooding. Emulsification of the displacement fluid and crude oil changes the viscosity of the displacement phase, modulating the mobility ratio and forming an oil wall, thereby increasing oil recovery. Generally, oil displacement efficiency can be increased by approximately 6% after emulsion flooding (Zhang Lidong. Research on Self-emulsifying System Oil Displacement Formulations, [Master's Thesis]: Daqing Petroleum Institute, Daqing: 2007). However, if the emulsification capacity of the flooding system is too strong, not only does it increase the amount of oil displacement agent required, but excessive emulsification can also lead to problems such as difficulty in demulsifying the produced fluid. Therefore, the search for a flooding system that is moderately emulsified within the formation while easily demulsified upon surface recovery has become a hot topic of research.

[0006] In recent years, research has focused on enhancing oil recovery through spontaneous or in-situ emulsification within formations. Chinese patent CN110173244B discloses an in-situ emulsification and thickening system with controllable viscosity and its application in water-flooded reservoirs. By adding an emulsifier, ultrafine colloidal particles, and an appropriate amount of suspending agent, this system achieves controlled viscosity. The core technology is to control the viscosity of the flooding system through viscosity control, aiming to effectively drive the efficient development of water-flooded reservoirs. However, the patent does not disclose whether it ensures that the produced emulsion is easily demulsified.

[0007] Chinese patent CN110079291B discloses an in-situ emulsification and viscosification system containing a high phase transition point and its application in water-flooded oil reservoirs. By combining a water-soluble surfactant with an oil-soluble surfactant, and then adding an appropriate amount of a carrier and colloidal particles, the system achieves in-situ emulsification and viscosification, thereby improving the development of water-flooded heavy oil reservoirs. However, the patent does not disclose a method for achieving bidirectional emulsification control, nor does it disclose experimental results on demulsification of produced fluids.

[0008] Therefore, for the research on composite flooding technology for conglomerate oil reservoirs, it is necessary to optimize the composition of the oil displacement system formula according to the characteristics of the formation fluid, crude oil properties, clay characteristics and injection volume, so that it can be emulsified as highly as possible in the formation and as low as possible in the ground processing system, thereby realizing dynamic regulation of emulsification during the composite flooding process.

[0009] Therefore, it is very necessary to develop an oil displacement system with controllable interfacial tension and emulsification that can solve the above technical problems. Summary of the Invention

[0010] In order to solve the technical problems of conventional composite flooding systems, such as the inability to maintain low interfacial tension throughout the entire process and the inability to regulate emulsification capacity in both directions, the present invention provides a composite flooding system in which interfacial tension and emulsification degree can be artificially controlled. This flooding system does not experience co-precipitation of oppositely charged surfactants and can achieve low interfacial tension (<5×10 -2 mN / m), the emulsification capacity can be artificially controlled, and the produced fluid is easy to demulsify. The present invention is mainly used for the project of significantly improving the recovery rate of binary composite flooding (SP) in conglomerate oil reservoirs.

[0011] The present invention is a technical improvement based on the control of factors affecting the interfacial tension and emulsification capacity of the oil displacement system. In response to the drawbacks of petroleum sulfonates in binary flooding field tests, namely insufficient interfacial tension reduction capacity and inability to manually control the emulsification degree during the oil displacement process, the present invention first utilizes the high reactivity of alkylbenzyl chlorides and adopts a spacer insertion method to synthesize a series of long-chain alkylphenyl gemini quaternary ammonium salt oil-soluble surfactants by controlling appropriate reaction conditions. The anionic petroleum sulfonates and cationic long-chain alkylphenyl gemini quaternary ammonium salts are then mixed, and the strong interaction principle of anionic and cationic surfactants is utilized to optimize the ratio of the two surfactants with opposite electrical properties, thereby preventing precipitation and maintaining a low interfacial tension state throughout the oil displacement process. An appropriate amount of emulsification regulator and thickener are then compounded, allowing the adsorption capacity to be automatically adjusted according to the characteristics of the reservoir fluid, making the emulsification degree manually controllable.

[0012] The present invention is achieved through the following technical solutions:

[0013] An oil displacement system with controllable interfacial tension and emulsification, comprising the following components in percentage by weight:

[0014] Water-soluble surfactant: 0.2%-0.3%;

[0015] Oil-soluble surfactant: 0.001%-0.003%;

[0016] Thickener: 0.12%-0.15%;

[0017] Emulsifying regulator: 1%-2%;

[0018] The balance is water.

[0019] Preferably, the water-soluble surfactant is petroleum sulfonate KPS. It is obtained by sulfonation of naphthenic base oil. When using petroleum sulfonate KPS alone, under the same conditions, its minimum interfacial tension is 8×10 -2 On the order of mN / m.

[0020] Preferably, the thickener is a partially hydrolyzed polyacrylamide polymer with an average molecular weight of 20 million to 25 million.

[0021] Preferably, the emulsifying agent is an organic base, ethanol, isopropyl alcohol or dried sludge from an oilfield wastewater treatment station. When using sludge emulsifying agent, it must be stirred thoroughly to ensure that it is evenly dispersed in the oil displacement system.

[0022] More preferably, the organic base is triethanolamine.

[0023] Preferably, the water is produced water from the formation of the oil field test area or the adjacent blocks, and is obtained after purification by a water treatment system.

[0024] Preferably, the oil-soluble surfactant is a long-chain alkylphenyl gemini quaternary ammonium salt. Due to its oil solubility, the long-chain alkylphenyl gemini quaternary ammonium salt oil-soluble surfactant of the present invention cannot form ultra-low interfacial tension when used alone, and a large amount of insoluble matter exists in the solution, which affects the injectivity of the oil displacement system.

[0025] More preferably, the long-chain alkylphenyl gemini quaternary ammonium salt includes at least one of didodecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt, ditetradecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt and dihexadecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt.

[0026] More preferably, the preparation method of the long-chain alkylphenyl gemini quaternary ammonium salt comprises the following steps:

[0027] (1) dissolving N,N,N',N'-tetramethylethylenediamine and long-chain alkylbenzyl chloride in ethanol and subjecting the mixture to reflux reaction to obtain a reaction mixture;

[0028] (2) Add acetone to the reaction mixture, let it stand and remove the upper layer. The yellow viscous liquid in the lower layer is the long-chain alkylphenyl gemini quaternary ammonium salt.

[0029] More preferably, the long-chain alkylbenzyl chloride includes at least one of dodecylbenzyl chloride, tetradecylbenzyl chloride and hexadecylbenzyl chloride.

[0030] More preferably, in step (1), the molar ratio of N,N,N',N'-tetramethylethylenediamine to long-chain alkylbenzyl chloride is 1:2-1:3.

[0031] More preferably, the reflux reaction temperature in step (1) is 75° C.-78° C., and the reaction time is 18 h-24 h.

[0032] More preferably, in step (2), acetone is added to the reaction mixture in 2-4 portions.

[0033] The present invention also relates to the application of the above oil displacement system in conglomerate oil reservoirs.

[0034] Preferably, the properties of the conglomerate reservoir are as follows: the conglomerate reservoir temperature does not exceed 70°C, the formation water salinity is 10,000 mg / L < 20,000 mg / L, the formation crude oil viscosity is < 100 mPa·s, and the average formation permeability is greater than 30×10 -3 μm 2 , weak water-sensitive characteristics in reservoirs.

[0035] The beneficial effects of the present invention are:

[0036] In the indoor evaluation experiment, the oil displacement system of the present invention can achieve the lowest interfacial tension with the crude oil in the test area of ​​6×10 -4mN / m order of magnitude, the equilibrium interfacial tension can be maintained at 5×10 -3 On the order of mN / m.

[0037] The interfacial tension and emulsification controllable oil displacement system provided by the present invention can maintain low interfacial tension throughout the field test. The oil-water interfacial tension of the produced fluid from 85% of the central wells in the test block can reach 10 -2 mN / m; the emulsification regulator provided by the present invention can control emulsification throughout the entire process, making the produced fluid easy to demulsify and having a certain clay swelling prevention effect. In indoor core flooding experiments, it can achieve a recovery rate of over 20%, and in field tests, the recovery rate of the entire test area has increased by more than 15%.

[0038] The preparation method of the long-chain alkylphenyl gemini quaternary ammonium salt provided by the present invention has a product yield of more than 90%, few reaction steps, simple process and is suitable for large-scale production.

[0039] The present invention compounds petroleum sulfonate KPS and long-chain alkylphenyl gemini quaternary ammonium salt, and can reduce the crude oil / water solution interfacial tension to 6×10 -4 mN / m, while under the same conditions, the interfacial tension of only using petroleum sulfonate KPS can only reach 8×10 -2 mN / m order of magnitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the infrared spectrum of dodecylphenyl gemini quaternary ammonium salt TR12 in Example 1.

[0041] Figure 2 This is the interfacial tension test result of Example 4.

[0042] Figure 3 This is the emulsification effect of the modified system and the original composite system in Example 5.

[0043] Figure 4 The oil phase volume of different flooding systems after dilution with formation water at different times.

[0044] Figure 5 It represents the emulsification state at different production stages of the same oil well.

[0045] Figure 6 It is the emulsified state of the oil displacement system during the displacement process.

[0046] Figure 7 This shows the oil production increase after the oil displacement system was injected into the central well. DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, and such modifications and replacements fall within the scope of protection of the present invention.

[0048] Instruments used in each example: spinning drop interfacial tension meter, TX500C, USA; microscopic oil displacement model: provided by Beijing Hitech Petroleum New Technology Development Center; liquid chromatograph, Agilent 1260, USA.

[0049] Reagents: ethanol, isopropanol, triethanolamine, analytical grade, Beijing Yili Fine Chemicals Co., Ltd.

[0050] Long-chain alkylbenzyl chloride was prepared according to the literature (Wang Yu, Zheng Xiaoyu, Wu Zhaoliang. Study on chloromethylation of dodecylbenzene catalyzed by N(C2H5)3HCl-2ZnCl2 ionic liquid [J]. Acta Petrolei Sinica (Petroleum Processing), 2007, 23(2): 12-16);

[0051] N,N,N',N'-Tetramethylethylenediamine, analytical grade, Zhangjiagang Hanbadu Chemical Co., Ltd.;

[0052] Petroleum sulfonate KPS, produced by Xinjiang Jinta Investment (Group) Co., Ltd.;

[0053] Partially hydrolyzed polyacrylamide (HPAM), average molecular weight 20 million, from Beijing Hengju Oilfield Chemical Reagent Co., Ltd.

[0054] The crude oil was obtained from the central well of the binary flooding test area in Karamay Oilfield. The contents of saturated hydrocarbons, aromatic hydrocarbons, non-hydrocarbons, and asphaltene were 78.54%, 8.62%, 7.82%, and 2.14%, respectively. The viscosity was 20.6 mPa·s, and the acid value was 0.1 mg KOH / g oil.

[0055] Formation water, taken from the central well of the binary flooding test area in Karamay Oilfield, has the following composition: HCO3 - :2991.69mg / L,Cl - :3109.84mg / L,SO4 2- :42.80mg / L,Ca 2+ :154.81mg / L,Mg 2+ :36.95mg / L,Na + +K + :3210.05mg / L, mineralization is 9099.88mg / L.

[0056] Example 1

[0057] (1) Synthesis of long-chain alkylbenzyl chloride: 0.1 mol dodecylbenzene, 30 mL cyclohexane, 30 mL acetic acid, 1 mmol cationic gemini phase transfer catalyst G were added to 0.08 mol N(C2H5)3HCl-2ZnCl2 ionic liquid in sequence. 12-6-12 , 0.30 mol paraformaldehyde. Freshly prepared hydrogen chloride gas was slowly introduced, stirred, and the temperature was raised to 55°C for 10 hours. After the reaction was completed, the reaction solution was poured into a separatory funnel, and the lower ionic liquid layer was removed. The upper liquid was washed sequentially with deionized water, saturated Na2SO4, saturated NaHCO3, and deionized water until neutral. The upper liquid was dried over anhydrous MgSO4 and filtered to obtain a light yellow liquid. The cyclohexane was removed by rotary evaporation to obtain homemade dodecylbenzyl chloride.

[0058] Similarly, by changing the reaction raw material dodecylbenzene to tetradecylbenzene or hexadecylbenzene, and following the same reaction conditions, homemade tetradecylbenzyl chloride and hexadecylbenzyl chloride can be obtained respectively, which can be used as raw materials for synthesizing gemini quaternary ammonium salts of different chain lengths.

[0059] (2) Synthesis of didodecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt: In a 250 mL four-necked flask equipped with a reflux condenser and a thermometer, 0.05 mol of N,N,N',N'-tetramethylethylenediamine, 0.15 mol of dodecylbenzyl chloride (prepared), and 60 mL of ethanol were added in sequence, and the temperature was gradually raised to 75°C and refluxed for 24 h.

[0060] (3) After the reaction is completed, the mixture is cooled to room temperature, and 30 mL of acetone is added to the reaction mixture three times. The mixture is allowed to stand for a long time, and the upper organic layer is removed. The yellow viscous liquid at the lower layer is dodecylphenyl gemini quaternary ammonium salt TR12 (i.e., didodecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt).

[0061] Its infrared spectrum is attached Figure 1 . Figure 1 Medium, 2923cm -1 and 2857cm -1 , is the stretching vibration of -CH2; 1744cm -1 is the stretching vibration of benzylaldehyde; 1604cm -1 、1497cm -1 It is the vibration of C=C skeleton of benzene ring; 1458cm -1 Deformation vibration of -CH2; 1373cm -1 Deformation vibration of -CH3; 1228cm -1 is CN stretching vibration; 1024cm -1 is C-Cl stretching vibration; 888cm -1 , 826cm-1, 758cm-1 is the out-of-plane bending vibration of the aromatic ring; 726cm -1 Yes - (CH2) n The presence of a small amount of benzylaldehyde in the product is due to the use of NaCO3 to wash out excess acidic substances during the preparation of the raw material benzyl chloride, which readily hydrolyzes the benzyl chloride to benzylaldehyde. The presence of chlorinated hydrocarbons in the product is due to incomplete conversion of the benzyl chloride. Based on the reaction raw materials and reaction principle, it can be inferred that the product of Example 1 is a quaternary ammonium salt surfactant.

[0062] Example 2

[0063] The same operation and raw material ratio as in Example 1 were performed, except that dodecylbenzyl chloride was replaced with tetradecylbenzyl chloride, the volume of the ethanol solvent was increased to 70 mL, and the reaction temperature and reaction time were unchanged to obtain tetradecylphenyl gemini quaternary ammonium salt TR14 (i.e., ditetradecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt).

[0064] Example 3

[0065] The same operation and raw material ratio as in Example 1 were performed, except that dodecylbenzyl chloride was replaced with hexadecylbenzyl chloride, the volume of the ethanol solvent was increased to 80 mL, the reaction temperature was increased to 78 ° C, and the reaction time was unchanged to obtain hexadecylphenyl gemini quaternary ammonium salt TR16 (i.e., bis-hexadecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt).

[0066] Example 4

[0067] Petroleum sulfonate KPS and dodecylphenyl gemini quaternary ammonium salt TR12 (TR) were used as oil displacement agents. The solution was prepared with formation water to a total concentration of 0.25% and a weight ratio of KPS to TR12 of 249:1 and 247:3. 2% triethanolamine (OA) was added as an emulsifier and 0.12% partially hydrolyzed polyacrylamide (HPAM) was added as a thickener. The interfacial tension of crude oil from different oil displacement systems and the central well of the test area was measured at 40°C using a spinning drop interfacial tension meter. Using 0.25% petroleum sulfonate KPS alone, the interfacial tension could only reach 10 -1 mN / m; when using 0.25% TR12 alone, the interfacial tension increases from 0.008mN / m to 0.08mN / m within 30 minutes, and it cannot maintain a low interfacial tension for a long time, which obviously cannot meet the requirements of the binary flooding system formulation. When the cationic gemini surfactant TR and KPS are compounded, the interfacial tension can reach 10 at both concentration ratios. -3 mN / m, and the lowest interfacial tension reaches 10 -4 The order of mN / m shows a strong interaction between anions and cations. The interfacial tension test results are shown in the attached Figure 2 .

[0068] Example 5

[0069] Take petroleum sulfonate KPS and dodecylphenyl gemini quaternary ammonium salt TR12 (abbreviated as TR) as oil displacement agents, use formation water to prepare the liquid, the total concentration of the oil displacement agent is 0.25%, the weight percentage of KPS and TR12 is 249:1, and then add 2% of organic base (OA) triethanolamine as a regulator and 0.12% of partially hydrolyzed polyacrylamide HPAM as a thickener. This system is called the modified system, and the system without cationic gemini quaternary ammonium salt is called the original composite system. First, crude oil and formation sand (particle size less than 1mm) are mixed at a ratio of 5:1, and then the modified system (or original composite system) is mixed with oil-bearing formation sand at a ratio of 10:1, shaken on a shaker for 24 hours, and the emulsification condition is observed. The emulsification condition after standing for 7 days is as shown in the attached figure. Figure 3 As shown. Figure 3 It can be seen that the modified system (attached Figure 3 The emulsification degree of the original composite system (left) is not serious, no intermediate transition layer appears, and the mud and sand sink to the bottom of the test bottle; the original composite system without TR12 (attached Figure 3 Right) There is an emulsion layer, the water phase is turbid, some clay is dispersed in the water phase, and the clay particles and the middle emulsion layer are mixed together to form a relatively stable intermediate phase, indicating that TR12 has a certain effect in preventing over-emulsification and swelling.

[0070] Example 6

[0071] First, two types of flooding systems were prepared using formation water from the binary flooding test area: the original system: 0.25% KPS + 2% triethanolamine + 0.12% partially hydrolyzed polyacrylamide HPAM; the modified system: 0.247% KPS + 0.003% TR12 + 2% triethanolamine + 0.12% HPAM. 20 mL of the flooding system was taken and diluted with the formation water used for preparation according to a certain volume ratio (the volume of the flooding system and the volume of the formation water were 9:1 and 6:4). Then, 6 mL of crude oil from the test area was added at an oil-water ratio of 3:7. The total volume of the oil-water mixture was 20 mL. The mixture was stirred at 40 °C and allowed to stand for a long time after being fully shaken. The thickness of the oil layer or emulsion layer was recorded at different lengths of time. The results are shown in the attached figure. Figure 4 shown.

[0072] When the oil displacement system is injected into the formation, it is inevitably diluted by the formation water, and its water distribution reflects the emulsification condition of the formula system when it migrates in the formation. The binary oil displacement system of 0.25% KPS + 2% triethanolamine + 0.12% HPAM has a very strong emulsification ability at a dilution ratio of 9:1, which is reflected in the strong emulsification ability of the oil displacement system when it just enters the formation; the emulsification ability is reduced after the dilution ratio of 6:4, which is reflected in the emulsification ability of the oil displacement system after it penetrates into the formation and is diluted by the formation water. In general, the emulsification ability of the oil displacement system without TR12 is higher than that of the system with TR12. The change in the emulsification condition of the latter is the unique feature of the present invention. By adding strongly interacting cationic gemini surfactants, the excessive emulsification of the oil displacement system is prevented. Controlling moderate emulsification can not only improve the crude oil recovery rate, but also effectively prevent the excessive emulsification of the produced fluid and the difficulty of demulsification. Appendix Figure 5 After verifying the application of the emulsification-controlled flooding system, the emulsification status of the produced fluid at different production stages (from left to right, initial, mid-term, and late stages) was shown. In the same binary flooding well, the degree of emulsification varied with the volume of the flooding system injected. However, after sufficient quiescence, the oil and water separated easily and essentially on their own, with no excessive emulsification that made demulsification difficult, demonstrating the effectiveness of the emulsification control method of the present invention.

[0073] Example 7

[0074] The dynamic emulsification process of the oil displacement system was observed on an indoor microscopic oil displacement model. The formulation system (0.247% KPS + 0.003% TR12 + 2% triethanolamine + 0.12% HPAM, prepared with formation water) was tested at a temperature of 40°C.

[0075] Experimental process: First, the microscopic etched model was evacuated with a vacuum pump for 2 hours; the formation water was saturated and replaced with the prepared simulated oil to establish the bound water saturation; the crude oil in the microscopic etched model was displaced with injected water until residual oil was formed; the composite oil displacement stage was carried out, and the entire displacement process was observed. The flow process and various phenomena in the experiment were recorded with color microscopic video and microscopic photography. The experimental results are attached. Figure 6 Attached Figure 6 (Left) is the emulsified state of the oil displacement system and crude oil during the oil displacement process. Figure 6(Right) is the distribution of residual oil after the displacement is completed. The oil displacement system provided by the present invention has a high emulsification strength throughout the entire displacement process. Under the action of various chemical agents in the oil displacement system, it can be seen that the interfacial tension of large oil droplets is reduced under the action of surfactants, the oil blocks are deformed and elongated, and then eroded into small oil droplets, and further emulsified into small oil droplets, forming an oil-in-water emulsion that moves forward with the composite agent. At this time, the oil displacement effect is the best, and it is also the main stage of composite agent oil displacement. It is this emulsification and erosion effect that partially peels off the large oil blocks that cannot pass through the throat. This process is repeated, and eventually, the large oil blocks are displaced. After this stage of displacement, there is very little residual oil in the pores passed by the composite agent. At the end of the oil displacement process, the remaining oil adheres to the surface of the pores and pores in the form of a residual oil film. This embodiment fully illustrates that the oil displacement system provided by the present invention can play the role of moderate emulsification throughout the entire process.

[0076] Example 8

[0077] Ethanol, n-butanol, and n-pentanol were added to the formulation (0.247% KPS + 0.003% TR12 + 0.12% HPAM, prepared with formation water) to a concentration of 2 wt%. The system was then shear-emulsified for 1 minute to induce shear degradation of the polymer (simulating formation shear). The oil-to-water ratio was fixed at 1:1, and the temperature was maintained at 40°C. Changes in the oil phase volume were observed. 1 wt%, 2 wt%, and 3 wt% of oil sludge (derived from dehydrated oily sludge from a sewage treatment plant) were added to the crude oil. The effects of the sludge on the emulsification properties of the displacement system were investigated under the same conditions and methods. The emulsification parameters were calculated after 6 hours of oil-water mixing. The emulsification index is defined as the ratio of the difference between the initial oil phase volume and the oil phase volume at 6 hours to the initial oil phase volume. The experimental results are shown in Table 1.

[0078] As can be seen from Table 1, adding ethanol can improve the emulsification degree of the oil displacement system. After adding n-butanol and n-pentanol, the emulsification capacity decreases, and the oil sludge generated in the produced fluid output process can reduce the emulsification capacity of the formula system. Therefore, the oil displacement system proposed by the present invention can be regulated from the indoor experimental results. Because in the oil displacement process, KPS, TR and alcohol have chromatographic separation, and the oil displacement system will carry the formation clay together due to the higher emulsification capacity after just entering the formation, which can reduce the emulsification strength of the oil displacement system. In addition, the formula system will also reduce the emulsification strength after being diluted by formation water. Therefore, the oil displacement system of the present invention will not make the produced fluid emulsification serious. In addition, after adding n-pentanol, asphaltene will be precipitated out, which may clog the formation during actual application.

[0079] Table 1 Effects of several additives on the emulsification strength of the oil displacement system

[0080]

[0081] Example 9

[0082] The formula system (0.247% KPS + 0.003% TR12 + 0.12% HPAM + 2% triethanolamine OA, prepared with formation water) was used to conduct a displacement experiment on a one-dimensional core in the laboratory at a temperature of 40°C. The experimental results are shown in Table 2. At the same time, the dynamic monitoring results of the binary flooding field test (the formula used is the same as that of the indoor study) are tracked and monitored. The results are shown in Appendix Figure 7 Reservoir parameters in the binary flooding test area: formation temperature 40°C, formation permeability mainly distributed in the range of 10×10 -3 μm 2 ~500×10 -3 μm 2 The average permeability is 90×10 -3 μm 2 The formation crude oil viscosity ranged from 22 mPa·s to 59 mPa·s, and the formation water salinity ranged from 9000 mg / L to 13000 mg / L. The KPS concentration in the central well's produced fluid and the corresponding oil-water interfacial tension were measured. The results are shown in Table 3.

[0083] The KPS concentration detection method is implemented according to the method provided in the literature (Chen Quansheng: Study on the distribution coefficient of petroleum sulfonates in oil and water phases during ASP flooding [J]. Oil and Gas Recovery Technology, 1997, 4 (1): 11-15). The three parallel experiments increased the recovery rate by more than 20%, indicating that the present invention significantly improved the recovery rate. During the long-distance flow of the binary flooding chemical system, after the dilution of groundwater, the distribution of oil and water phases, the adsorption and retention of rocks and clay minerals, the oil-water interfacial tension of 85% of the central wells still maintained a low interfacial tension order of magnitude. Appendix Figure 7 The beneficial effects of the present invention are fully demonstrated: before injection into the flooding system, the produced fluid contained over 80% water. After injection into the flooding system, the water content rapidly dropped to between 50% and 75%. After the flooding system injection was stopped, the water content slowly increased. After injection into the flooding system, the central well showed a significant oil-increasing effect, with the single-well calibration increasing the recovery factor by over 17%. The data in Table 3, based on field tests of binary composite flooding, demonstrate that the interfacial tension-controlled formulation system provided by the present invention exhibits excellent compatibility with reservoir fluids and rock clay minerals. The KPS flooding agent achieves moderate recovery and maintains high efficiency over long distances.

[0084] Table 2 One-dimensional core flooding results of binary composite system

[0085]

[0086] Table 3 Petroleum sulfonate concentration in produced fluid and oil-water equilibrium interfacial tension

[0087]

[0088] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. An oil displacement system with controllable interfacial tension and emulsification, characterized in that: According to weight percentage, it is composed of the following components: Water-soluble surfactant: 0.2%-0.3%; Oil-soluble surfactant: 0.001%-0.003%; Thickener: 0.12%-0.15%; Emulsifying regulator: 1%-2%; The balance is water; The water-soluble surfactant is petroleum sulfonate KPS; The thickener is a partially hydrolyzed polyacrylamide polymer; The emulsifying regulator is an organic base, ethanol, isopropanol or dried sludge from an oilfield sewage treatment station, and the organic base is triethanolamine; The oil-soluble surfactant is a long-chain alkylphenyl gemini quaternary ammonium salt, which includes at least one of didodecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt, ditetradecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt and dihexadecylphenyl-tetramethylethylenediamine gemini quaternary ammonium salt.

2. The oil displacement system according to claim 1, characterized in that The average molecular weight of the partially hydrolyzed polyacrylamide polymer is 20 million to 25 million.

3. The oil displacement system according to claim 1, characterized in that The water is produced water from oilfield formations and is obtained after purification treatment.

4. The oil displacement system according to claim 1, characterized in that The preparation method of the long-chain alkylphenyl gemini quaternary ammonium salt comprises the following steps: (1) Dissolving N, N, N', N'-tetramethylethylenediamine and long-chain alkylbenzyl chloride in ethanol and subjecting the mixture to reflux reaction to obtain a reaction mixture; (2) Add acetone to the reaction mixture, let it stand and remove the upper layer. The lower layer is the long-chain alkylphenyl gemini quaternary ammonium salt.

5. The oil displacement system according to claim 4, characterized in that: The long-chain alkylbenzyl chloride includes at least one of dodecylbenzyl chloride, tetradecylbenzyl chloride and hexadecylbenzyl chloride.

6. The oil displacement system according to claim 4, characterized in that: In step (1), the molar ratio of N, N, N', N'-tetramethylethylenediamine to long-chain alkylbenzyl chloride is 1:2-1:

3.

7. The oil displacement system according to claim 4, characterized in that: The reflux reaction temperature in step (1) is 75°C-78°C and the time is 18-24 hours.

8. The oil displacement system according to claim 4, characterized in that: In step (2), acetone is added to the reaction mixture in 2-4 portions.

9. Use of the oil displacement system according to any one of claims 1 to 8 in conglomerate reservoirs.

10. The use according to claim 9, characterized in that The properties of the conglomerate reservoir are as follows: The temperature of the conglomerate reservoir does not exceed 70°C, the salinity of the formation water is less than 10,000 mg / L and less than 20,000 mg / L, the viscosity of the formation crude oil is less than 100 mPa·S, and the average permeability of the formation is greater than 30×10 -3 μm 2 , weak water-sensitive characteristics in reservoirs.

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